Not surprisingly, land adjoining the beach in Santa Monica is so expensive that young couples can only afford to hold their wedding receptions there, not to a raise a family there. Indeed, Santa Monica as whole, with its exquisite weather, is unaffordable by all but the wealthiest young families. There just isn't a large supply of land when you start at 1 Pico Blvd., you can only drive in directions covering 180 degrees. The other 180 degrees are underneath the Pacific Ocean.
Also, as my theory of Affordable Family Formation would predict, Santa Monica is famously liberal -- e.g., the joke about it being the People's Republic of Santa Monica. Jane Fonda's ex-husband Tom Hayden represented the Santa Monica area in the state legislature for 18 years. Republican "family values" campaign themes don't go over big in Santa Monica. The people who raise kids in Santa Monica can afford to insulate them with private schools, tutors, and all the rest. They don't need politicians' help in making it a little easier to raise their kids.
Another famous example of the interrelationship between coastlines, density, and liberalism is found within the city of Chicago. In the city, population density increases exponentially as you approach the lakefront. In time-honored Chicago political jargon, the voters who live in that narrow strip of high-rises are known as "Lakefront Liberals."
I might add, however, that America's Gulf Coast is largely an exception to the pattern of liberalism increasing as you approach the coasts, which works well for the Pacific, the Great Lakes, and much of the Atlantic.
I think the difference is that the Gulf Coast doesn't have as many major urban areas set directly on the ocean, perhaps due to danger from hurricanes. For example, Galveston, a classic seafront city, was obliterated by a hurricane in 1900, killing 6,000. So, the population center of the Texas coastal region moved 45 miles inland (and 45 crucial feet above sea level) to Houston. So, Houston can expand 45 miles in any direction before its exurbs run into saltwater. Hence, Houston has low housing prices and conservative voters.
Also, before air conditioning, the climate was so deplorable for four months of the year along the Gulf Coast that it discouraged urbanization. (British government employees once got the same tropical hardship pay for manning the British consulate in Houston as they did for working in Lagos, Nigeria.)